1. Related Art
Dramatic improvements in semiconductor integration densities have largely been achieved through corresponding improvements in semiconductor manufacturing technologies. As semiconductor manufacturing technologies move into the deep submicron era, the semiconductor industry is considering a number of new technologies, such as extreme ultraviolet (EUV) lithography and massively parallel electron beam lithography. Unfortunately, these technologies are not ready for production as yet.
The spacer-is-dielectric (SID) self-aligned double-patterning (SADP) process is a technology that can increase integration densities using today's process technologies. This technology uses two masks and a spacer deposition step to realize features on a wafer. It is desirable to be able to determine mask layouts to print complex design intents using an SID SADP process.
2. Summary
Some embodiments described in this disclosure provide methods and apparatuses for determining a mandrel mask layout and a trim mask layout based on a design intent. In some embodiments, the design intent includes two-dimensional patterns that correspond to a circuit design that implements an arbitrary logic function. The mandrel mask layout and the trim mask layout can be used in an SID SADP process to print the design intent on a wafer. In this disclosure, unless otherwise stated, the phrase “based on” means “based solely or partly on.”
During operation, a system can determine whether a graph corresponding to a design intent is two-colorable. Each vertex in the graph can correspond to a shape in the design intent, and each edge in the graph can correspond to two shapes in the design intent that are separated by a space that is less than a pre-determined distance. Note that the minimum spacing that is allowed between two shapes can depend on various parameters associated with the shapes. In some embodiments, the minimum allowable spacing between two shapes can be determined based on a set of design rules. If the graph is not two-colorable, the system can merge one or more pairs of shapes in the design intent to obtain a modified design intent, so that a modified graph corresponding to the modified design intent is two-colorable. The system can then determine a two-coloring for the modified graph. Next, the system can place one or more core shapes in the mandrel mask layout which correspond to vertices in the modified graph that are associated with a selected color in the two-coloring. The system can then place one or more shapes in the trim mask layout for separating the shapes in the design intent that were merged.
In some embodiments, the system can identify a pair of shapes in the design intent that have a substantially minimum run length, wherein merging the pair of shapes resolves a coloring conflict. The system can then merge the pair of shapes in the design intent. Substantially minimizing the run length of the merged shapes can improve manufacturability of the design intent.
In addition to the core shapes, the system can place additional shapes in the mandrel mask layout to print one or more edges of the design intent that are not printed by the core shapes. In some embodiments, the system can merge and/or remove additional shapes in the mandrel mask to improve manufacturability of the design intent.
Specifically, in some embodiments, the system can identify a first additional shape and a second additional shape in the mandrel mask layout which are separated by a space that is less than a pre-determined distance. Next, the system can merge the first additional shape and the second additional shape.
In some embodiments, the system can identify an additional shape in the mandrel mask layout that is smaller than a pre-determined size, and remove the additional shape from the mandrel mask layout. In some embodiments, removing the additional shape effectively retargets the design intent. In some embodiments, the system may add one or more shapes in the trim mask layout to print one or more edges in the design intent that are not printed by the mandrel mask layout.